1. Field of the Invention
This invention relates to the art of bonding between ceramics and metals and more particularly, to a method for bonding ceramics and metals while preventing crackings of the ceramics.
2. Description of the Prior Art
Broadly, known methods of bonding ceramics and metals together include (1) an adhesive method, (2) a metallizing method and (3) a spray coating method. However, these methods have the following drawbacks.
(1) The adhesive method is the simplest method but adhesion strength at high temperatures is low.
(2) The metallizing method is a method which comprises placing an Mo metallic powder such as Mo, Mo-Mn or the like on ceramics, heating the powder for metallizing in a moistening atmosphere, subjecting the metallized layer to Ni plating, and bonding a metal to the ceramic by brazing. However, this method is disadvantageous in difficulty of application depending on the type of ceramic. In addition, because of the high metallizing temperature, great thermal stress is exerted on the ceramic upon cooling, with the unfavorable tendency toward cracking.
(3) The spray coating method is a method in which ceramic powder is fused and adhered to metals by spraying. The method is also disadvantageous in that the bonding strength is low and the sprayed ceramic becomes porous.
As will be seen from the above, the prior art methods have such drawbacks that the bonding strength is not adequate, ceramics are liable to crack, and limitation is placed on the type of ceramic being applied.